The present invention relates to a process for the regeneration of waste paper containing encapsulated constituents, so as to be able to recycle the paper in the form of a pulp. It relates more particularly to a process for the regeneration of waste no-carbon copying paper containing microcapsules.
Papers with encapsulated constituents in general contain compounds such as inks, pigments, dyestuffs or their precursors, covered by a film and in the shape of microcapsules. These papers are capable of producing a coloration when a pressure is applied. They can be obtained by various known techniques, such as those described in U.S. Pat. Nos. 2,505,470, 2,505,471, 2,505,472, 2,505,488 and 2,505,489 filed on Nov. 8, 1947 and assigned to The National Cash Register Co.
It is very awkward to regenerate waste paper of this type. Hitherto, such paper has been disintegrated in an alkaline medium and the pulp thus obtained has been subjected to a flotation treatment to remove from it the microcapsules containing the materials responsible for the coloration.
The paper pulps thus regenerated nevertheless exhibit colorations which vary greatly and are very difficult to remove. In fact, the presence of sodium hydroxide during the disintegration causes an at least partial destruction of the microcapsules, and hence causes the liberation of the materials responsible for the coloration, and accelerates their fixing to the fibres.
To avoid this advantage it has been proposed (French Patent Application No. 79/10,274 filed on Apr. 13, 1979 in the name of J. M. Voith G.m.b.H.) to effect the disintegration of waste paper of this type in the absence of any reactant.
In this case, again, a partial destruction of the microcapsules, by simple mechanical effect, can be observed, with the same disadvantages as in the process described above; alternatively, if the conditions are particularly gentle, only insufficient separation of the fibres is achieved and hence the microcapsules cannot be properly removed during the flotation stage, so that, during the subsequent treatments of the pulp, liberation of the colorants is observed.